Designed of circular photonic crystal fibers (C-PCFs) for guiding and controlling the orbital angular momentum of light

In this paper, we designed and simulated the circular photonic crystal fibers (C-PCFs) for guiding and controlling the orbital angular momentum (OAM) of light. The optimum parameters in C-PCFs were archived by considering the conditions that eliminate the spin-orbit coupling for each guided mode. Moreover, for optical communication applications, a flat modal dispersion is required for a wide wavelength range from 1.25 to 2 µm and the OAM modes must have a low confinement loss. For different fractions of air filling (f), the results were simulated and compared to achieve the best values of f. According the simulated results, the proposed design of C-PCF can support a group of OAM modes up to HE51 and EH31 with topological charge of l=4. Furthermore, our C-PCF shows high quality in terms of dispersion and OAM mode losses, which can additionally be used in space-division multiplexing rather than the conventional wavelength-division multiplexing for optical communication systems.